Thank you, I think I see what you mean, but I would highly appreciate if you could comment on whether I understood you correctly.
Say the customer's current site is http://www.customer.com
(it's a functioning site, and the customer wants it to function until the moment when the redesigned site is fully ready). This site has nothing to do with my server at the moment (it is hosted elsewhere), and the name servers of customer.com domain are not the name servers of my ispconfig server.
For the sake of clarity I'll repeat that once the redesigned site is ready the customer wants to change hosting from its current location to my ispconfig server, BUT keep the current name servers.
So - what do I need to do? I guess first I have to create a regular web site http://www.customer.com
at my ispconfig server, and make NO dns entries. Then when the redesigned site is ready, I'll just ask the customer to change the 'A' dns entries of customer.com to the value of the shared ip at which the site is set up at my ispconfig server - and everything should be OK.
So now there's only a question of how to be able to see the site in its development (before it is ready) on my ispconfig server.
Do I need to ask the customer to create a co-domain, say, test.customer.com - and have it point at the newly created site on my ispconfig server? In order for this to work I guess I must first create this co-domain myself (again, no dns entries).
So when the site is ready, I move the site from http://test.customer.com
to just http://customer.com
by moving all files from the "web/test" folder to "web" folder, and have the customer change the 'A' dns entry of customer.com to the value of the shared ip of my ispconfig server.
Will it work the way I described?